The vascularization of engineered tissues is critical to the ultimate success of tissue engineering as an organ replacement therapy. The formation of new capillary vessels in vivo, or angiogenesis, also is linked to the pathogenesis of numerous diseases including cancer, and is regulated by local cues within the tissue microenvironment. The general goal of this RENEWAL proposal is to understand the mechanism by which local extracellular matrix (ECM) properties regulate capillary endothelial cell proliferation, gene expression, and capillary tube morphogenesis required in angiogenesis. The investigator has found that adhesion to ECM cooperates with growth factors to generate not only biochemical, but also mechanical signals that are important in driving capillary endothelial cell function. Studies from the past grant period demonstrated that ECM stiffness and composition could be used to regulate proliferation, gene expression, and capillary tube formation by modulating contractile tension generated by the actin cytoskeleton. In this proposal, the investigator proposes to further investigate the role of these mechanical and adhesive cues in regulating angiogenic behaviors. Specific Aim 1 will be to investigate the role of ECM stiffness in regulating angiogenesis. Specific Aim 2 will be to investigate the role of ECM peptide ligands in regulating angiogenesis. Specific Aim 3 will be to investigate the role of spatial organization of the ECM in regulating angiogenesis. Together, these studies will define the mechanisms by which local structural and mechanical properties within ECM modulate endothelial cell function and capillary morphogenesis, and establish new strategies to promote angiogenesis in native ischemic tissues as well as in ex-vivo engineered tissues.